Calculate Speed of Car in Car Accident

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Discussion Overview

The discussion revolves around estimating the speed of a car involved in an accident based on limited information, specifically the distance from the point of impact to where the car stopped, the mass of both cars, and the final velocity of 0 m/s. The scope includes theoretical reasoning and practical estimation methods.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the possibility of determining the speed of the other car given the limited data available.
  • Another participant suggests that while exact answers may be unattainable due to unknown factors, rough estimates could be made.
  • A participant mentions that police typically use skid marks to estimate speed, although this may not apply in this case due to the absence of skid marks.
  • One participant notes that the cars separated after the crash, indicating it was not a collision crash, which may complicate speed estimation.
  • Another participant proposes using the equation vf^2=vi^2 + 2ad to estimate the initial velocity, contingent on knowing the force of impact to determine acceleration, acknowledging that this would still be an estimate due to other influencing factors.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of estimating the speed, with some suggesting it may be possible under certain conditions while others emphasize the challenges posed by unknown variables. No consensus is reached on a definitive method or conclusion.

Contextual Notes

The discussion highlights limitations such as the absence of skid marks, the lack of known acceleration, and the reliance on force estimates, which may affect the accuracy of any speed calculations.

gca114
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Recently I have been involved in a car accident, and would like to figure out what was the speed of the other car that crashed into us.

I only have two figures, the distance from the point of impact to where the car stopped and the mass (of both cars); and also, the final velocity which is 0 m/s.

Does someone think that this is possible to figure the speed of the other car that crashed into us?
 
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Too many unknown factors for getting an exact answer.

Some rough estimates can be possible.

Please search forum, this question is asked every few months.
 
gca114 said:
Recently I have been involved in a car accident, and would like to figure out what was the speed of the other car that crashed into us.

I only have two figures, the distance from the point of impact to where the car stopped and the mass (of both cars); and also, the final velocity which is 0 m/s.

Does someone think that this is possible to figure the speed of the other car that crashed into us?

I think the police use the skidmarks of the tyres to work out the speed at which the car was travelling. And other stuff. They probably have the best estimate of anyone.
 
There were no skidmarks.. as there was not a chance for breaks.. also.. it wasn't a collision crash... both cars separated from each other after the crash..
 
Well let's see. You can use the equation vf^2=vi^2 +2ad
you have vf, you say that you have distance, you don't have acceleration but if you knew with how much force the car hit you with you can figure out accelartion from F=MA and then you can find Vi. Therefor if you can figure out the force of impact it can be done. This of course would be an estimate as some other factors are involved.
 

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